Hydroprocessing can include processes which convert hydrocarbons in the presence of hydroprocessing catalyst and hydrogen to more valuable products. Hydrocracking is a hydroprocessing process in which hydrocarbons crack in the presence of hydrogen and hydrocracking catalyst to lower molecular weight hydrocarbons. Depending on the desired output, a hydrocracking unit may contain one or more beds of the same or different catalyst. Hydrocracking can be performed with one or two hydrocracking reactor stages.
A hydroprocessing recovery section typically includes a series of separators in a separation section to separate gases from the liquid materials and cool and depressurize liquid streams to prepare them for fractionation into products. Hydrogen gas is recovered for recycle to the hydroprocessing unit. A stripper column for stripping hydroprocessed effluent with a stripping medium such as steam is used to remove unwanted hydrogen sulfide and other light gases from hydroprocessed liquid streams before product fractionation.
Hydroprocessing recovery sections comprising fractionation columns rely on external utilities that originate from outside of the hydroprocessing unit to provide heater duty to vaporize the fractionation materials. Fractionation sections that rely more on heat generated in the hydroprocessing unit than external utilities are more energy efficient.
In some regions, diesel demand is lower than demand for lighter fuel products. Distillate or diesel hydrocracking is proposed for producing the lighter fuel products such as naphtha and liquefied petroleum gas (LPG).
There is a continuing need, therefore, for improving the efficiency of processes for recovering fuel products from hydrocracked distillate stocks.